How does the Intoxilyzer 9000 distinguish alcohol from other substances?

The Intoxilyzer 9000 distinguishes alcohol, specifically ethanol, from other substances by using specific wavelengths of light that are uniquely absorbed by ethanol. This principle is based on infrared spectroscopy, where the device shines infrared light through a sample of breath. Different substances absorb infrared light at different wavelengths, allowing the Intoxilyzer 9000 to identify the presence of alcohol based on its unique absorption characteristics.

This method provides a reliable means of detecting alcohol concentration in a breath sample while reducing the likelihood of interference from other compounds. By focusing on the specific absorption patterns associated with ethanol, the device can accurately quantify the concentration of alcohol without being significantly affected by other components present in the breath.

In contrast, the other methods mentioned in the options do not describe the operating principle of this device. Chemical reaction methods and gas chromatography, while valid techniques for analyzing substances, are not employed by the Intoxilyzer 9000. Additionally, measuring breath pressure changes does not provide the specificity required to accurately identify and quantify ethanol in the presence of other compounds.